Strabismus is a disorder in which the visual axes are not properly aligned. If a monocular strabismus persists through the "plastic" period of visual system neurodevelopment, a temporary suppression of the image from the deviating eye can become permanent resulting in amblyopia. Treatment for amblyopia after age five or six rarely results in reestablishment of optimal visual acuity. Strabismus, and its resulting amblyopia, are significant public health problems, especially in young children. Prevalence estimates range up to 6.5% in young children. Strabismus accounts for over 50% of all amblyopia and a significant proportion of all non-amblyopic strabismus cases will have deficiencies in binocular vision. The long term objectives of this research are to identify etiologic factors for childhood strabismus and develop intervention techniques and programs that will prevent this disorder, or at the very least, maximize its early detection so appropriate treatment can be instituted. The specific aims of this project are to examine the role of prenatal, neonatal, and maternal factors on the risk to strabismus; to examine the role of family history on the risk to strabismus; and to quantify differences in these characteristics in cases who develop amblyopia and those who do not. The general design of this study will be an epidemiologic case-control study of strabismus in children 0-6 years of age. Incident cases will be ascertained from both hospital patients and the private practices of ophthalmologists in the Baltimore area. Controls will be selected from the labor/delivery logs at the cases' hospital of birth. Data will be collected from the cases' diagnostic medical record, cases' and controls' birth medical records, mothers' obstetric medical records, and an interview with the mother of all cases and controls. Appropriate analyses will be done to examine the association of prenatal, neonatal and maternal characteristics with strabismus. Analyses will also be done to compare the distribution of these risk factors between those cases of strabismus who developed amblyopia and those who did not, stratified by type of strabismus.